Hot melt compositions comprising styrene-isobutylene copolymer,wax,and a primary resin

ABSTRACT

A SOLID, HOMOGENEOUS AND ESSENTIALLY RANDOM COPOLYMER OF STYRENE AND ISOBUTYLENE HAVING A NUMBER AVERAGE MOLECULAR WEIGHT OF FROM ABOUT 1000 TO ABOUT 4000, A HETEROGENEITY INDEX OF FROM ABOUT 1.50 TO ABOUT 2.25 AND A STYRENE CONTENT OF FROM ABOUT 40 TO ABOUT 90 WEIGHT PERCENT WITH ITS HIGHER MOLECULAR WEIGHT FRACRIONS HAVING A HIGHER STYRENE CONTENT THAN THE AVERAGE CONTENT OF THE COPOLYMER.

United States Patent 3,835,079 HOT MELT COMPOSITIONS COMPRISING STY-RENE-ISOBUTYLENE COPOLYMER, WAX, AND A PRIMARY RESIN Frank Scardiglia,Arlington Heights, and Takeo Hokama,

Chicago, Ill., assignors to Velsicol Chemical Corporation, Chicago, Ill.

No Drawing. Application Oct. 29, 1970, Ser. No. 85,297,

now Patent No. 3,757,000, which is a continuation-inpart of abandonedapplication Ser. No. 728,332, May 10, 1968. Divided and this applicationJan. 22, 1973, Ser. No. 325,500

Int. Cl. C08f 45/52 US. Cl. 260-285 A 13 Claims ABSTRACT OF THEDISCLOSURE A solid, homogeneous and essentially random copolymer ofstyrene and isobutylene having a number average molecular weight of fromabout 1000 to about 4000, a heterogeneity index of from about 1.50 toabout 2.25 and a styrene content of from about 40 to about 90 weightpercent with its higher molecular weight fractions having a higherstyrene content than the average styrene content of the copolymer.

This is a division of application Ser. No. 85,297, filed Oct. 29, 1970,now 3,757,000, which is a continuation-inpart of our copendingapplication Ser. No. 728,332, filed May 10, 1968, now abandoned.

This invention relates to new copolymers of styrene and isobutylene topreparational methods therefor and to novel resinous compositionscontaining such copolymers. More particularly, this invention relates tohomogeneous highly random low molecular weight copolymers of styrene andisobutylene which are obtained according to a specific preparationalmethod.

The polymerization of styrene and isobutylene to form copolymers is Wellknown and several classes of these copolymers have been preparedutilizing different prepara tional conditions and procedures. Most ofthese copolymers are of the low temperature type, that is, they havebeen prepared at polymerization temperatures below 0 C., usually below40 C. and frequently within the range of 80 C. to 150 C. These lowtemperature polymers are typically characterized by a combined styrenecontent usually having an upper limit of about 65 to 70 weight percentand by a high molecular weight ranging from about 100,000 to 500,000 interms of Staudinger units which is necessary for the obtainment of theirdesired properties of elasticity and high tensile strength. Othercopolymers have been prepared at temperatures above 0 C. ranging up toas high as 200 C. These copolymers are characterized by a relatively lowcombined styrene content usually ranging up to about 40 weight percentand, more significantly, by their normally liquid or oily nature whichrenders them useful as lubricant or lubricating oil, and blendingagents. It has now been discovered that another class'of novelcopolymers of styrene and isobutylene can be prepared at polymerizationtemperatures above 0 C. by utilizing a specific, preparational methodwhich produces such copolymers in almost theoretical yield and moreoverin a convenient and highly desirable industrial manner.

Accordingly, an object of this invention is to provide a new class ofcopolymers of styrene and isobutylene. Another object is to provide aunique preparational method for obtaining this class of copolymers. Afurther object is to provide a method for producing these copolymers inhigh yield and in a particularly desirable industrial manner. A stillfurther object is to provide novel r "Ice.

resinous compositions containing these copolymers which are particularlyuseful as hot melt resins or pressure sensi tive adhesives. These andother objects of this invention will be apparent from the followingfurther detailed description thereof.

The copolymers of this invention are highly homogeneous and essentiallyrandom, normally solid copolymers of styrene and isobutylene which havea low molecular weight, a broad molecular Weight distribution and a highweight content of styrene. These copolymers are further characterized bya combination of several other properties or characteristics such as aparticular heat softening point range, optical clarity, thermalstability and a high degree of solubility in solvents and compatibilitywith other polymers and polymer systems. Due to this desirablecombination of characterizing properties, the copolymers of thisinvention are particularly useful for a variety of polymericapplications. For example, the copolymers can be used as modifiers toimprove the physical properties of other polymers or polymer systems andas components of resinous compositions such as hot melt resins or pressure s'ensitive adhesives.

The copolymers of this invention are capable of having a high content ofstyrene ranging up to as high as 90 or more, usually 70 to weightpercent. Yet they are still highly homogeneous at such levels in thatthe copolymers are composed essentially of styrene and isobutylenecopolymer units to the substantial exclusion of either styrene orisobutylene homopolymer units. The styrene content of the copolymerranges from as low as about 40 to as high as about 90 weight percentwith the corresponding isobutylene content ranging from about 60 toabout 10 weight percent. The preferred copolymers, however, contain arelatively high content of styrene within the range of from about 45 toabout weight percent styrene with the particular amount within thisrange being dependent upon the ultimate intended use of the copolymer.For example when the copolymer is intended for use in hot melt resins,the preferred styrene content ranges from about 60 to about 85 weightpercent and when it is intended for use in pressure sensitive adhesivesthe preferred styrene content ranges from about 40 to 75 weight percentstyrene. This high concentration of styrene is usually difficult toachieve especially when copolymers of highly uniform composition aredesired consisting essentially of styrene and isobutylene copolymerunits to the substantial exclusion or absence of any styrene homopolymerunits. Nevertheless, such uniform, highly homogeneous copolymers arereadily achieved in essentially quantitative yields when preparedaccording to the preparational method of this invention as hereafterdescribed.

The molecular weight of the copolymers of this invention incontradistinction to the typical copolymers of styrene and isobutyleneis very low and moreover must be within a limited range in order thatthe copolymers possess the desired set of properties. As used hereinmolecular Weight is described both in terms of the weight averagemoleculg weight M and the number average molecular weight M,,. However,unless specified to the contrary, when used herein and in the appendedclaims, molecular weight will mean the number average molecular weight MThe significance of these conventional molecular weight terms as well asmethods for their determination are more fully described in theStructures of Polymers," M. 1. Miller, Reinhold, New York, 1966. Ingeneral, the molecular weight of the copolymers of this invention canrange from about 1000 to about 4000. A more limited molecular weightrange, however, which is readily achieved by utilization of thepreparational method of this invention is preferred and ranges fromabout 1200 to 3500. This latter limited range is particularly preferredin that the copolymers having this low molecular weight range areespecially suitable for use in various applications such as componentsof resinous compositions useful as hot melt resins or pressure sensitiveadhesives.

In addition to a limited, low molecular weight range, the copolymers ofthis invention have a broad molecular weight distribution. Thisdistribution of the molecular Weights of the copolymer may be describedconventionally in terms of a heterogeneity index which is defined as theratio of the weight average molecular weight to the number averagemolecular weight, H /H Usually, the heterogeneity index, lT /fi for thecopolymers can range from about 1.50 to about 2.25. Typically, however,for copolymers having the preferred molecular weight, the heterogeneityindex ranges from about 1.65 to about 2.15, especially for copolymersintended for use as components of resinous compositions.

As indicated, the copolymers of this invention are characterized by ahigh degree of randomness, that is, the copolymers consist essentiallyof basic repeating units of the following formula:

wherein m and n are integers from 1 to about 15, and the styrene andisobutylene moieties are distributed in an essentially random manner.Furthermore, the above basic repeating unit is located along the polymerchain in an essentially random distribution. The total number ofdescribed basic repeating units in the copolymer is such that the numberaverage molecular weight is from about 1000 to about 4000. Thus thepolymers of this invention do not contain long sequences of styrene orisobutylene units, nor do they contain long sequences of alternatingstyrene and isobutylene units. This distinguishes the copolymers of thepresent invention from block-type copolymers which essentially containlong sequences of styrene and isobutylene units along their molecularchain. It also distinguishes the copolymer from a graft-type copolymerwhere repeating units of either styrene or isobutylene are attached to abackbone chain of the other. In addition to indicating the random natureof the copolymer of this invention the above formula also serves toillustrate the specific nature of the copolymer in that there aresubstantially no ring alkylated styrene residues in the polymer arisingfrom an in situ alkylation of the styrene by the isobutylene and furtherthat the polymerization of the isobutylene unit takes place so thatthere are two methyl groups and not only one perpendicular to themolecular chain.

The styrene-isobutylene copolymers of this invention are furthercharacterized in that their high molecular weight fractions have ahigher styrene content than the average styrene content of the copolymerand their lower molecular weight fractions correspondingly have a lowerstyrene content than the average styrene content of the copolymer.Essentially, the styrene content of the higher molecular weightfractions will be up to about 5 Weight percent higher than the averagestyrene content of the copolymer and the lower molecular Weightfractions will have a styrene content up to about 5 weight percent lessthan the average styrene content of the copolymer.

The styrene-isobutylene copolymers of this invention, as

indicated, are normally solid materials and have relative- 1y high heatsoftening points. As measured by the ring and ball method, the heatsoftening point of the copolymers can range from about 125 F. to about225 F. A more limited range of from about 130 F. to about 225 F. andespecially from about 190 to 225 F. is preferred, however, formaximizing the usefulness of the copolymers in such applications aspolymer modifiers or components of resinous compositions used for hotmelt resins. A further and important characterizing property of thecopolymers of this invention is that they have good thermal stabilityand are stable against chemical decomposition at temperature above 350C. Accordingly, they can be suit ably employed in applications withoutdecomposition where high temperatures are likely to exist or occur. Thisis particularly important on such polymer applications as hot meltresinous compositions which are conveniently subjected to elevatedtemperatures during their application.

The copolymers of this invention also possess and are characterized by ahigh degree of optical clarity. This in turn is partially a function ofthe compositional uniformity of the copolymers in that they are composedessentially of copolymer units without substantial proportions of anyhomopolymer units. In fact, the optical clarity of the copolymers can beused to a certain degree as an indicator of their highly homogeneousnature. The optical clarity of the copolymers is manifested by highlight transmission in that the copolymers permit light to pass throughfilmcastings of the copolymer without substantial proportions of thelight being absorbed or reflected. For example, normally printed mattercan be readily read through a filo;1 casting of the copolymer having athickness of 0.5 we

As indicated, the copolymers have the important property and are furthercharacterized by a high degree of solubility in various solvents such ashexane, mineral spirit, or aliphatic hydrocarbons. In addition to thisproperty of high solubility, the copolymers can be further characterizedas being highly compatible with a variety of different polymers andcopolymer systems. For example, the copolymer, when blended with suchpolymers as styrene-butadiene rubbers, acrylics or alkyds formhomogeneous, stable, one phase polymer systems.

While the copolymers of this invention can be defined by reference tothe above characterizing properties such as molecular Weight, molecularweight distribution, randomness and compositional homogeneity, as wellas softening points, such properties are a function of or interrelatedto their specific method of preparation. Accordingly, the copolymerscan, in addition to such properties, also be defined or characterized byreferences to such method of preparation. In preparing the copolymersaccording to this invention, a specific preparational method should beutilized in order that all of the above described properties be obtainedespecially in the preferred ranges. Utilization of such method,moreover, not only permits the obtainment of the desired copolymers, butin addition achieves such result With almost theoretical conversions andin a particular convenient and desirable industrial manner. Thispreparational method involves an interrelated combination of processmgfeatures which basically comprise an elevated polymerizationtemperature, a particular catalyst system and a certain mode ofconducting the polymerization reaction. This method is effected, ingeneral, by gradually bringmg the styrene and isobutylene into reactivecontact, in the presence of a hydrocarbon polymerization solvent, with acatalyst system. of a primary catalyst and a cocatalyst whilemaintaining an elevated polymerization temperature.

The catalyst system which is utilized in the preparation 1s composed ofa primary catalyst and a co-catalyst which are maintained in a specific,relative proportion. Both the selection of the primary catalyst and thecocatalyst and their relative proportions in the catalyst system areimportant to the success of the method in producing high yields ofcopolymers having all of the ultimately desired properties. The primarycatalyst can consist of at least one alkyl aluminum dihalide wherein thealkyl portion can have from 1 to about 5 carbon atoms including, forexample, such groups as methyl,

ethyl, propyl, and butyl and the halide portion can be a halogen atomhaving an atomic Weight within the range of from about 35 to about 80including, for example, chlorine and bromine. Of the various alkylaluminum dihalides which can be employed, the preferred primary catalystis ethyl aluminum dichloride.

The co-catalyst utilized in combination with the primary catalyst in thecatalyst system comprises at least one material selected from the groupconsisting of water, an alkyl halide, a hydrogen halide or an alcohol.Examples of these co-catalysts include alcohols such as alkanols havingfrom 1 to about 5 carbon atoms in the alkyl portion of the molecule,such as ethyl alcohol, propyl alcohol, tertiary butyl alcohol ormixtures thereof; secondary or tertiary alkyl halides Where the alkylportion contains from about 3 to about 5 carbon atoms and where thehalide portion is the same as defined above, such as butyl chloride,propyl chloride or pentyl chloride; or a hydrogen halide such ashydrogen chloride or hydrogen bromide. Of the various catalysts whichcan be employed, an alkanol such as tertiary butyl alcohol or an alkylhalide such as tertiary butyl chloride and especially water arepreferred and particularly when used in combination with the preferredprimary catalyst, ethyl aluminum dichloride.

As indicated, the relative proportions or ratio of the co-catalyst tocatalyst in the catalyst system is important in achieving copolymershaving the desired set of properties. While this ratio can varydepending upon such factors as the particular catalyst and co-catalystused, it should be maintained within certain limits if copolymers of thedesired properties such as molecular weight and molecular weightdistribution are to be achieved. Generally, the co-catalyst should bepresent in the catalyst system within a range of from about 2 to 30 molpercent based upon the mols of the primary catalyst present. A morelimited range of from about 2.5 to 15 or about 5 to about mol percent ispreferred for such co-catalysts as water and particularly when used withthe preferred, primary catalyst, ethyl aluminum dichloride. The quantityof the primary catalyst used in the catalyst system which in turndetermines the quantity of co-catalyst can also be varied. Theparticular amount used is dependent upon such factors as the particularprimary catalyst, the co-eatalyst and the polymerization temperature.Generally, the quantity of the primary catalyst can range from about0.20 to about 1.5 weight percent based upon the combined weight of thestyrene and isobutylene monomers. A more limited range of about 0.25 to1.2 or about 0.5 to about 1.0 is preferred, however, when employingcatalyst systems containing ethyl aluminum dichloride in combinationwith co-catalysts such as water, alkyl halides or alkanols.

In preparing the catalyst system, the co-catalyst and the primarycatalyst can be admixed in the desired ratio prior to thepolymerization. More preferably, it can be prepared in the presence ofthe solvent just prior to polymerization by simply adding theappropriate quantities of catalyst and co-catalyst to the solvent withmixing. The primary catalyst itself can also be prepared in situ duringor just prior to the polymerization by combining the necessary materialsto form the desired alkyl aluminum dihalide. For example, aluminumchloride can be admixed with diethyl aluminum chloride in theappropriate proportion to form the active, preferred ethyl aluminumdichloride catalyst in situ. Generally, however, it is preferable to addthe primary catalyst as a relatively pure compound to the solventtogether with the cocatalyst just prior to the polymerization.

The temperature utilized in effecting the polymerization, as indicated,is unusually high for the polymerization of styrene and isobutylene toform normally solid copolymers. Nevertheless, this high temperature is anovel and important feature of the preparational method of thisinvention. Utilization of such high temperature in combination with thecatalyst system as well as with the mode of conducting thepolymerization permits the attainment of the unique copolymers of thisinvention having all of the desirable properties such as low molecularweight and a broad molecular weight distribution. Moreover, employmentof this elevated temperature allows the polymerization to be conductedin a highly convenient and desirable manner in that the extensivecooling, critical in elfecting the low temperature polymerization ofstyrene and isobutylene, is unnecessary. The polymerization temperaturecan range from about 10 to about 50 C. with the specific temperatureutilized within this range being dependent upon such factors as thecatalyst system employed, the solvent and the ultimately desiredproperties of the copolymer. Usually, however, a more limitedtemperature range is preferred of from about 15 to about 25 C. or about20 C. especially when preparing the preferred class of copolymersaccording to this invention.

The hydrocarbon solvent used to effect the polymerization can include awide class of hydrocarbon polymerization solvents. The particularsolvent employed in the polymerization, however, will affect theultimate properties of the copolymer produced. Accordingly, it isimportant to select a solvent or combination of solvents which providesa copolymer having the ultimately desired properties. The solvents whichcan be used individually or in combination include aliphatics such asalkanes containing from about 6 to about 10 carbon atoms per moleculesuch as hexane or heptane and aromatics such as benzene or alkylatedbenzenes such as toluene, xylene or ethyl benzene. Of the varioussolvents which can be utilized, preferred solvents are alkanes such ashexane or heptane or mixtures thereof. The quantity of solvent employedcan be varied but there should at least be a quantity of solvent presentsufficient to provide a readily stirrable reaction mixture. Typicallywhen using solvents such as hexane this amount ranges from about 0.5 toabout 2 weight parts or preferably equal Weight parts of solvent per'one weight part of the combined styrene and isobutylene charge.

In conducting the preparational method, another important processingfeature in combination with the features of the catalyst system andelevated polymerization temperature is the particular mode used to bringthe styrene and isobutylene into reactive contact with the catalystsystem. It is most important that the styrene and isobutylene begradually contacted with the catalyst system in the presence of thesolvent if the copolymers of the desired properties are to be achieved.This contacting is preferably effected by gradually adding both thestyrene and isobutylene to the solvent containing the catalyst sys temWhile maintaining the desired polymerization temperature. In graduallyadding the styrene and isobutylene, preferably admixed in a single feedstream, the time required to complete the addition will vary dependingupon such factors as the particular catalyst system and thepolymerization temperature utilized and to a lesser degree upon thescale of the reaction. Generally, however, the styrene and isobutyleneshould be added at a rate adjusted so that they are substantiallycompletely polymerized upon contact with the catalyst system leavingsubtantially no unreacted monomer in the reaction mixture. Typically,this addition time can range from about 0.10 to 2 hours with additiontimes of from about 0.5 to 1.5 or about 1.0 hours being preferred formaximizing the desired properties of the copolymers produced. The chargestream of styrene and isobutylene gradually added to the mixture ofsolvent and catalyst system can contain styrene in an amount of fromabout 40 to 90 weight percent. However, when preparing the preferredcopolymers according to this invention, the charge contains styrene inan amount ranging from about 45 to weight percent.

The polymerization method of this invention can be conducted in a batch,semi-batch or continuous operation.

A batch operation is usually suitable, however, and one illustrativeprocedure involves gradually adding a single stream of styrene andisobutylene monomers, admixed in the desired weight ratio, to thestirred solvent containing the appropriate catalyst system. The gradualaddition of the styrene and isobutylene is regulated so thatsubstantially all of the styrene and isobutylene are polymerized uponcontact with the catalyst system leaving substantially no unreactedmonomer in the reaction mixture. During the addition, the temperature ofthe exothermic reaction is maintained Within the desired range byutilizing appropriate cooling means. When the addition of the monomersis complete, the coplymer product can then, if desired, be recoveredfrom the reaction mixture. It is generally desirable, however, to leavethe coplymer in the recation mixture in the presence of the catalystsystem at the polymerization temperature for a residence periodsuflicient to insure total, uniform polymerization. The length of thisresidence period can range from only a few minutes to one hour or more.Typically, residence periods ranging from about 0.25 to 3 hours aresufiicient with about 0.75 to 2.5 or about 1 hour usually beingpreferred.

After the copolymer has been in contact with the catalyst system for asuflicient residence period it can be removed from the reaction mixtureand purified according to several different procedures. Advantageously,the removal procedure involves first eliminating the catalyst systemfrom the reaction mixture by adding a solid adsorbent to adsorb thecatalyst and the solids can then be eliminated as a solid filtrate.Alternatively acidic or basic materials can be added to form watersoluble adducts of the catalyst. Such adducts can then be removed bywater washing of the reaction mixture. After the catalyst system hasbeen eliminated by one of the above procedures or a combination thereof,the solvent and any impurities formed in the polymerization can bereadily removed from the reaction mixture by distillation at reducedpressure, leaving the desired copolymer in high yield.

As indicated, the styrene-isobutylene copolymers of this invention areuseful for a variety of different polymeric applications. ()neespecially useful application is utilization of the copolymers ascomponents of resinous compositions used for hot melt resins. These hotmelt resinous compositions are typcially composed of an admixture of aprimary resin component, a wax component and a modifying resin componentwhich serves to compatibilize and otherwise improve the properties ofthe primary resin and wax component. These hot melt resin compositionsare used primarily in coating and adhesive applications. For example, incoating applications they are used to coat sub strates such as cloth,paper or cardboard to provide a moisture and vapor impermeable coatingor surface and in adhesive applications they are used to bond layers ofpaper or cardboard to form laminates of such materials which possessgreat strength as well as being impervious to Water or moisture vapors.A particular requirement of these hot melt resinous compositions is thatthey have a desirable combination of melting points and viscosities ormolten viscosity which permits them to be machine applied at high speedto the particular substrates. Aside from such basic properties, however,these resins must, as films or coatings, also have a combination ofother suitable properties such as low water vapor transmissivity,strength, elasticity, glossiness, thermal stability, good adhesivenessand hot tack, as well as good color.

A hot melt resinous composition having a particularly desirable set ofthese properties is obtained according to this invention by utilizingthe novel styrene-isobutylene copolymers as the modifying resincomponent of such resinous compositions in combination with the primaryresin and the wax component. The primary resin component which can becombined with the wax component and the styrene-isobutylene copolymer toform the hot melt resinous compositions of this invention can include awide variety of different materials. Generally, most of the materialscommonly employed as the primary resin component of hot melt resins canbe suitably utilized. Typically, these materials include polyethylenes,polypropylenes, ethylene-vinyl acetate copolymers or asphalts or variouscombinations thereof. Usually, ethylene-vinyl acetate copolymers arepreferred as the primary resin component and suitable copolymers ofethylene and vinyl acetate which can be employed have a melt index inthe range of 2.5 to 150 using the ASTM Procedure D-1238. Thesecopolymers advantageously contain a vinyl-acetate monomer content in therange of from about 5 to 45 weight percent and more typically from about15 to about 42 weight percent. The wax component which can be compoundedwith the primary resin component and with the styrene-isobutylenecopolymer can be selected from a wide group of Waxes and waxcombinations. Suitable waxes include aliphtic hydrocarbon waxes, forexample, parafiin waxes of various melting points ranging from about F.to about 165 F.; microcrystalline and crystalline waxes having meltingpoints of from about 165 F. to about 200 F.; natural vegetable waxes,such as carnauba or beeswax; or synthetic waxes such as hydrogenatedcastor oils or polyethylene oxides. Of the various Waxes which can beutilized as the Wax component, however, paratiins are generallypreferred. This is especially the case when employed in combination Withan ethylene vinyl-acetate copolymer as the primary resin, since theparaffins yield better moisture proofing and are generally lighter incolor. Frequently, it is desirable to employ the paraffin wax incombination with microcrystalline waxes especially when increasedadhesiveness is desired. These preferred parafiins have melting pointsin the range of about F. to about F.

The particular styrene-isobutylene copolymer compounded With the primaryresin and Wax component to form the hot melt resinous composition ofthis invention can be varied, with the particular copolymer employedbeing dependent upon such factors as the intended application of theresinous composition, for example coating or adhesive, the type ofproperties desired for such application, and the type of the Wax andprimary resin admixed with the copolymer. In general, thestyrene-isobutylene copolymer used in the resinous compositions intendedfor both adhesive and coating applications should have a styrene contentof from about 60 to about 85 weight percent styrene with a range ofabout 70 to 80 weight percent being preferred. Also, for both types ofapplications, the copolymer should have a certain molecular weightrange. Usually this molecular weight should range from about 2000 toabout 3200 with a range of from about 2100 to about 3000 generally beingpreferred to maximize the desired properties of the hot melt resinouscomposition containing the styrene-isobutylene copolymers. Inassociation with these molecular Weights the copolymer should also havea broad molecular Weight distribution and in terms of the heterogeneityindex H /fi the index should range from about 1.60 to about 2.10 with arange of from about 1.65 to about 2.00 being preferred. The ring andball heat softening point for these styrene-isobutylene copolymerspreferentially employed in the hot melt resinous composition of thisinvention usually range from about 180 F. to about 225 F. with a morelimited range of from about F. to 220 F. being especially preferred.

The particular formulation of the hot melt resinous composition of thisinvention in respect to the proportions of the primary resin component,the Wax component and the styrene-isobutylene copolymer can be widelyvaried. The particular proportions for any formulation are selecteddepending upon such factors as: the intended application of the resinouscomposition, for example coating or adhesive; the desired properties ofthe resinous composition for such applications, for example hot tack,clarity or flexibility; and the particular wax, primary resin andstyrene-isobutylene copolymer used. Usually for most hot melt resinapplications, the styrene-isobutylene copolymer can constitute fromabout 10 to about 85 weight percent of the resinous composition. A morelimited range of from about 20 to about 40 weight percent is especiallypreferred for resinous compositions where the primary resin componentconsists essentially of an ethylene-vinyl acetate copolymer and the waxcomponent consists essentially of a paraffin. The amount of the waxcomponent and primary resin component in the resinous composition canalso be varied. Generally the quantity of the primary resin can rangefrom about 1 to about 75 weight percent of the resinous composition witha range of about to about 35 weight percent usually being preferred andthe quantity of the wax component can range from about to about 90weight percent with a range of from about to about 75 weight percentgenerally being preferred. If desired the resinous hot melt compositionof this invention can contain other materials conventionally employed inhot melt resins such as dyes, pigments, oxidation inhibitors, ultraviolet stabilizers or bactericides in addition to the primary resincomponent, the wax component and the styrene-isobutylene copolymers.

The hot melt resinous composition of this invention can be prepared orformulated by employing conventional resin blending procedures. Theseprocedures typically involve mixing, blending or milling the components,if necessary under application of heat, in the desired respectiveproportion to obtain a substantially homogeneous, one phase orcompletely dispersed mixture. The hot melt resinous compositions thusprepared can be applied according to standard coating and adhesivetechniques to such substrates as cloth, paper or cardboard to formmoisture impermeable coatings or laminates of such materials having highstrength and water vapor imperviousness.

As indicated, another useful application of the styreneisobutylenecopolymers of this invention is their utilization as a component ofresinous compositions useful for pressure-sensitive adhesives. Thesepressure-sensitive adhesives may be defined as an adhesive materialwhich adheres tenaciously upon application of only light finger pressureand can be removed cleanly from the surface upon which they are applied.These pressure-sensitive adhesives are used for a variety of differentpurposes. Most commonly, however, they are used to formpressuresensitive adhesive tapes by application of the adhesivecomposition to a substrate tape comprising such materials as cloth,paper or a polymeric film. Typically, these pressure-sensitive adhesivesare composed of an elastomer component and a tackifier component. Inorder that these adhesive materials be suitable as pressure-sensitiveadhesives, they must possess the minimum requirements of wetting abilityor quick stick, good cohesiveness and good adhesiveness in the properrespective balance.

A pressure-sensitive, resinous adhesive composition having the properbalance of these properties is obtained according to this invention byutilizing the novel styreneisobutylene copolymers as the tackifyingcomponent of such resinous compositions in combination with theelastomer component. The elastomer component which can be combined withthe copolymer of this invention can include a wide variety of differentmaterials. Generally, most of the materials commonly employed as theelastomer component of pressure-sensitive adhesives can be suitablyutilized. Typically, these elastomer materials include rubbery materialssuch as reclaimed rubbers, natural rubber, styrene butadiene rubber,polyisobutylene or butyl rubber, or butadiene acrylonitrile rubber,block copolymer of styrene and butadiene or styrene and isoprene, orpolyvinyl ethers and polyacrylate esters, or various combinationsthereof. Of the various elastomeric materials which can be employed, therubbery elastomers such as natural rubber are preferred.

The particular styrene-isobutylene copolymer compounded with theelastomer to form the pressure-sensitive adhesive compositions of thisinvention can be varied with the particular copolymer employed beingdependent upon such factors as the intended adhesive application, thetype of properties intended for such application and the type ofelastomer compounded with the copolymer. In general, thestyrene-isobutylene copolymer should have a styrene content of about 40to about 75 weight percent with a range of from about 45 to 65 weightpercent being preferred. The copolymer used should have a certainmolecular weight range. Usually it should range from about 1500 to above2500 with a range of from about 1800 to 2200 generally being preferredto maximize the desired properties of the pressure sensitive adhesivecontaining the styrene-isobutylene copolymer. In association with thesemolecular weights the copolymer should also have a broad molecularweight distribution. In terms of the heterogeneity index H /I/T thecopolymers should have an index ranging from about 1.60 to about 2.25with a range of about 1.65 to about 2.15 generally being preferred. Thering and ball heat softening points for these styrene-isobutylenecopolymers preferentially employed in the pressure-sensitive adhesivecompositions of this invention usually range from about F. to about 225F. A more limited range is usually preferred, however, and ranges fromabout F. to about 180 F.

The particular formulation of the pressure sensitive adhesivecompositions of this invention in respect to the proportions of thecopolymer tackifier and the elastomer can be widely varied. Theparticular proportions for any formulation, however, are selected inconsideration of such factors as the intended adhesive application ofthe composition, the desired properties of the composition for suchapplications, for example, quick stick, adhesiveness and cohesiveness,and the particular elastomer and copolymer utilized. Usually for mostpressure sensitive adhesive applications, the styrene-isobutylenecopolymer can constitute from about 20 to about 80 weight percent of theadhesive composition with an amount of from about 50 to about 75 weightpercent being preferred. If desired, the adhesive compositions of theinvention can contain other materials conventionally employed inpressure-adhesive compositions such as plasticizers, fillers andantioxidants.

The pressure-sensitive adhesive compositions of this invention can beprepared or formulated by employing conventional techniques. One typicalprocedure for preparing these compositions and especially those intendedas a coating for flexible substrates to form pressure-sensitive adhesivetapes involves first forming solvent mixtures of the elastomer and thecopolymer admixed in the desired weight ratio. The solvent mixture isthen applied to a substrate employing standard coating techniques suchas casting followed by drying to remove the solvent.

The following examples are offered to illustrate the novel copolymers ofthis invention, the method of preparation and resinous compositionscontaining the copolymers. They are not intended, however, to limit theinvention to the particular copolymers, preparational procedures orresinous compositions illustrated.

EXAMPLE 1 A series of copolymers were prepared according to thisinvention by the following procedure:

Anhydrous hexane in an amount substantially equal in weight to thecombined weight of the styrene and isobutylene to be polymerized wascharged under a nitrogen atmosphere to a polymerization vessel equippedwith an addition funnel, stirring and cooling means and an overheadcondenser. The catalyst system was added by first charging a co-catalystto the hexane with stirring followed by the addition of the primarycatalyst consisting of freshly prepared substantially pure ethylaluminum 1 1 dichloride contained in heptane or hexane. After stirringfor a period of time sufiicient to insure adequate formation anddispersion of the catalyst system in the hexane, a premixed chargestream of styrene and isobutylene adjusted to the desired weight ratiowas gradually added 12 In Table II, the molecular weights reported weredetermined using Gel Permeation Chromatography techniques employingabsolute molecular weight standards determined by Vapor PressureOsmometry techniques. The thermal degradation temperature, that is thetemperature over a controlled addltion time via the additlon funnel 5 atwhich the copolymer chemically decomposes under apwhlle maintalmng thedes1red polymerization temperature plication of heat, was determinedusing Dlfferential Scanby cooling. After the add1t1on was complete, thestirring nmg Calorimetry techmques. The heat softening point was wascontinued for a residence period sufiicient to lnsure obtamed by theRing and Ball Method of AST M E28-58T.

TABLE I Primary catalyst weight Co-catalyst percent Polym- Styrenelbased M01 percent erizaisobutylene upon based upon tion Addi-Resimonomer combined mols tempertion dence Copolyrner weight monomerprimary atnre, time, time, Yield, number ratio weight Type catalyst 0.min. min. percent 50/ 50 l. H20 20 20 70 60 96 50/50 0. 1120 5-10 20 00180 96 50/50 0. 5 H20 10-32 60 90 90.7 50/50 0.5 H 7 20 00 60 92.0 /500.5 H10 7 20 00 00 94.5 50/50 0.5 H20 5 20 40 00 90.0 00/40 0. 5 H20 520 30 00 95 00/40 0.5 H20 5 20 30 00 /40 0.5 H20 10 20 05 00 99 00/400.5 H20 5 20 01 05/35 0.5 H20 5 20 00 60 94. 2 05/35 0.5 H20 5 20 00 6094 65/35 0.5 H20 5 20 30 60 97.5 /30 0. 5 H20 10 20 00 00 70/30 0.5 H205 20 50 00 70/30 0.5 H20 5 20 30 00 92.5 70/30 0.5 H20 3 20 60 00 93. 570/30 0.5 H20 5 20 00 00 95 75/25 1.0 t-Bu Cl 20 20-25 65 60 92 75/250.25 t-Bu OH 20 20-25 25 60 98.6 75/ 25 1. 0 H20 10 20 30 60 83 75/250.5 H20 5 19-22 27 00 99 75/25 1.0 H10 2.5 19-23 29 60 75/25 1.0 H20 1019-20 30 00 97 75/25 0.5 H20 7 19-20 30 99 75/ 25 0. 25 B20 10 18-23 30120 96 75/25 0.5 H20 2.5 10-24 35 120 80/ 20 0. 5 H20 7. 5 20-23 60 12096 50/20 0. 5 H20 5 19-21 60 120 TABLE II Weight Number average averageHetero- Heat Thermal molecular molecular geneity softening degraweight,weight, index, point, dation, Oopolymer number MW Mn Mw/Mn F. 0.Appearance 2, 100 Clear, water white. 2,450 Do. 1,750 Do. 2,000 Do.2,075 Do. 2,100 Do. 2, 000 D0. 2,000 Do. Do. 2,150 Do. 2,100 Do. 2 100Do. 2, 150 D0. 2 650 2,850 2,225 Do. 275 D0. 2, 705 D0. 1,250 Cleaig,yellowish. D- 2, 200 2. 07 215 401 Clear, water white. 2, 700 1. 09 205399 D0. 2, 450 1. 98 207 400 Do. 2, 400 1. 93 207 402 D0. 2, 400 1. 90209 352 Do. 2, 325 1. 92 206 367 Slight haze, Water white. 2,400 2. 05D0. 2,125 1. 87 213 307 Do. 2, 750 1. 90 218 402 Clear, slight yellow.

total and complete polymerization. The catalyst system was then removedby adding ethyl alcohol and solid 69 E MPLE 2 To demonstrate the randomnature of the copolymers of this invention the following example iscited. A copolymer was degraded using lauryl peroxide and thedegradation products were analyzed according to the following procedure:

About 50 grams of hexane, and 4.0 grams of lauryl peroxide were chargedto a sealed flask together with about 50 grams of copolymer No. 27 ofExample 1. This copolymer analyzed by nuclear magnetic resonancespectroscopy was composed of 77.87 weight percent styrene. The mixturewas heated at 70 C. for about 20 hours. During this period samples ofthe mixture were taken at intervals of 1, 2, 4 and 20 hours. Theindividual samples were filtered through a column of an acid acting clayto remove acidic compounds and the filtrate was distilled at 1 to 4 mm.Hg pressure to a pot temperature of 225 C. The distilled samples werethen analyzed by infrared spectroscopy for structural characteristics.The infrared spectra of all of the samples were substantially the same.This indicated that the copolymer is essentially random in nature andhas no block copolymer characteristics of large blocks of polystyrene orpolyisobutylcne or any graft polymer characteristics of substantialchains of either polystyrene or polyisobutylene grafted to a backbone ofthe other.

EXAMPLE 3 To demonstrate the random nature of the copolymers of thepresent invention, the homogeneity of the resin composition and theunexpected compositional variation in the molecular weight fractions,samples of copolymers prepared by the present process were fractionated(A) by mixed solvent precipitation and (B) by extraction with solventsof varying polarity, as follows:

Procedure A.To a five percent solution of the copolymer resin inbenzene, methanol was added dropwise until an opalescent solution wasobtained. The precipitated resin was allowed to settle and thesupernatant liquid was decanted. The precipitated resin was washed withmethanol and dried. The methanol solution was added dropwise to thedecanted supernatant solution to obtain another opalescent solution.Repeated precipitation and isolation of resin samples from solventmixtures containing increasing methanol concentration were carried outto give the results obtained in Table HI for two resins prepared by themethod of this invention.

Procedure B.A two percent suspension of copolymer resin of the presentinvention in isopropyl alcohol was refluxed for one hour. The hotalcohol solution was decanted from the insoluble portion of thecopolymer sample. The hot isopropyl alcohol solution was allowed tostand overnight at room temperature to precipitate the insoluble portionof the resin sample. The precipitated resin sample was filtered. Thefiltrate was concentrated to dryness to obtain an alcohol solublefraction. The results obtained by this procedure are reported in TableIII.

14 EXAMPLE 4 The copolymers of Example 1 were utilized to prepare hotmelt resinous compositions by blending the respective copolymer with aprimary resin and a wax. The primary resin component consistedessentially of an ethylene-vinyl acetate copolymer (Elvax 250, Du Pont)having an inherent viscosity of 0.85 at 30 C. (0.25 g./ ml. toluene) anda vinyl-acetate monomer content of about 27 to 29 Weight percent. Thewax component consisted essentially of a paraffin (Humble Oil, Parvan5010) having an ASTM melting point of about 151 F. The components wereblended to form a hot melt resinous composition containing differentproportions of the three components and as resins were subjected toseveral different tests to demonstrate their suitability as hot meltresinous compositions. The difierent resinous compositions prepared andtheir properties are summarized in the following Table IV. The datareported in Table IV were obtained using the following generalized testprocedures:

(A) Preparation of Resin Formulation (B) Thermal Stability A sample ofthe molten resin prepared as in Part A above, was placed in anelongated, small diameter glass tube. The glass tube was then sealed andplaced in a heated chamber maintained at 325 F. and stored under suchconditions for a period of about 1 hour. At the end of the period, theresin was observed for any phase separation of the three resincomponents.

(C) Tensile and Elongation A cast of the resin was prepared and stripsamples measuring 5 inches in length, 0.5 inch in width and havlng athickness of about mils were obtained substantially according to thegeneral procedure of ASTM 0638- 64-T, Type I. The samples were thentested on an Instron Tester using a CT Cell (5-250 1b.), a crossheadspeed of 2 in./min., and a jaw gap of 2 inches.

(D) Film Characteristics A thin film of the resin of Part A was preparedand was evaluated by hand for flexibility, elasticity, and toughness ona scale of good (G), fair (F), and poor (P).

(E) Molten Viscosity The viscosities of the formulations were obtainedusing a Contraves Rheometer Viscometer (Viscotemp, VT

model) equipped with a measuring beaker heated by recirculating oil.

(F) Moisture Vapor Transmission A paper substrate (glassine) was coatedwith the particular resinous composition at a rate of from about 8 to 12pounds of the resinous composition per ream and the moisture vaportransmission rate was determined using a Honeywell Water VaporTransmission tester.

TABLE IV lvois- Resin formulation, vsiiti weight percent Molten trans- PFilm characteristics viscositg Tensile (p.s.i.) Elonmission,

11 a gation H Thermal stabilit Oopolymer Copoly- Y mary Flexi- Elas-Tough- 300 F., N orni- Ruppercent 24 1 ml at 325 F., 1 hr. gartialnumber mer Wax resin bihty trcity ness centipoise n ture rupture 100 in.phase separation 33 50 17 F F F 444 470 478 17 No phase se araticn. 3350 17 G G G 566 496 496 11 Partial phasg separation. 33 33 33 G G G- 8,210 567 566 No phase separation. 20 50 30 G G G 2, 370 572 556 D 0. 2g11; g g 516 516 D0.

463 442 442 Partial phase separation. 33 33 33 G G G 8,892 614 598 N h20 50 30 G G G 2, 162 536 508 0 135. Separatwn 33 50 17 G G F 481 431431 Do.

a r s s s is 548 7 3 475 458 Slight phase separation. 33 33 33 F P P 7,063 610 534 N h 11' 33 50 17 P P P 518 481 481 0 133. Sepma Ion Z33 (I?(1% (1% 7, 545 534 39 1 Do.

572 556 41 Slight phase se aration. 20 50 30 G G G 2, 618 538 505 33 Nophase separation.

EXAMPLE 20 tion of from about 40 to 90 weight percent styrene at Thecopolymers of Example 1 were utilized to prepare pressure-sensitiveadhesive resinous compositions by blending the respective copolymer withan elastomer and the compositions thus prepared were used to formpressure-sensitive flexible tapes according to the following procedures:

Natural rubber stock (No. 1 Pale Crepe) was milled to a Mooney viscosity(ML 1+4 at 212 F.) of 45 to 50 and was then dissolved in heptane toprovide a concentration of to percent solids. This mixture was thencombined with the appropriate amount of a heptane solution of theparticular copolymer containing 20 percent solids to provide the desiredweight ratio of the copolymer to the rubber in the combined heptanemixture. This combined mixture containing the adhesive composition ofthe copolymer and the rubber elastomers was then applied to a thinflexible tape (Mylar, 1.5 mils). The coated tape was then dried toprovide a solvent-free film thickness for the adhesive compositionranging from about 1 to 2 mils. The dried tape was then subjected tocertain tests to demonstrate the suitability of the composition of thecopolymer and the elastomer as a pressuresensitive adhesive. The resultsof these tests are summarized in Table V. The tests employed wereconducted according to the standardized tests promulgated by thePressure Sensitive Tape Council, Glenview, Illinois, U.S.A. These testswere:

Peel Adhesion, P.S.T.C.N0. 1 Holding Power, P.S.T.C.No. 7

- Quick Stick, P.S.T.C.No. 5

In the aging test at 200 F., samples of the tape were placed in an ovenand maintained at 200 F. for seven days. At the end of the period, thetape samples were examined for any loss of tack or discoloration of theadhesive composition.

TABLE V Weight ratio, Peel adeo lyhesion Holding Quick 7-day Copolymermer elas- 180 F., power, stiek aging number tomer oz./i.n. min. ozJin.at 200 F.

2/1 33 165 23 No change. 2/1 17 l 3, 240 5. 5 Do. 2/1 16. 5 2 3, 240 2Do. 2/1 12 3 3, 240 0 D0.

1 in. creep at termination. 2 A in. creep at term nat on. 3 M5 in. creepat termination.

gradually contacting styrene and isobutylene in a propor-' apolymerization temperature of from about 10 C. to about 50 C. in thepresence of a hydrocarbon solvent with a catalyst system of an alkylaluminum dihalide primary catalyst and at least one co-catalyst selectedfrom the group consisting of water, an alcohol, an alkyl halide and ahydrogen halide, in an amount of from about 2 to about 30 mol percentbased upon the mols of the primary catalyst, maintaining the sytrene andisobutylene in reactive contact with the catalyst system for a timesuilicient to insure complete polymerization, and thereafter recoveringthe desired copolymer, from about 25 to about 75 Weight percent of Waxand from about 15 to about 35 weight percent of a primary resin selectedfrom the group consisting of polyethylene, polypropylene, ethylenevinylacetate copolymer, asphalt or combinations thereof.

2. The composition of Claim 1 wherein the copolymer has a number averagemolecular weight of from about 2000 to about 3200.

.3. The composition of Claim 1 wherein the copolymer has a styrenecontent of from about 60 to about weight percent.

4. The composition of Claim 1 wherein the copolymer lzialsoaheterogeneity index of from about 1.60 to about 5. The composition ofClaim 1 wherein the copolymer has a ring and ball heat softening pointof from about F. to about 225 F.

6. The composition of Claim 1 wherein the copolymer has a number averagemolecular weight of from about 2000 to about 3200, a styrene content offrom about 60 to about 85 weight percent, a heterogeneity index of fromabout 1.60 to about 2.10 and a ring and ball heat softening point offrom about 180 F. to about 225 F.

7. The composition of Claim 1 wherein the primary resin is polyethylene.

8. The composition of Claim 1 wherein the primary resin is an asphalt.

9. The composition of Claim 1 wherein the primary resin isethylene-vinyl acetate copolymer.

10. The composition of Claim 1 wherein the Wax is a paraflin.

11. The composition of Claim 6 wherein the primary resin isethylene-vinyl acetate copolymer.

12. The composition of Claim 1 wherein the styreneisobutylene copolymerhas a number average molecular weight of from about 2100 to about 3000,a heterogeneity index of from about 1.65 to about 2.00, a styrenecontent of from about 70 to 80 weight percent, and a ring and ball heatsoftening point of from about to about 220 F.

13. The composition of Claim 12 wherein the primary resin isethylene-vinyl acetate and the wax is a parafiin.

[References on following page) 17 18 References Cited 2,730,519 1/ 1956Leary 260-88.2 C 2,213,423 9/1940 Wiezevich 260-4 AR UNITED STATESPATENTS 2,643,993 6/1953 Tegge 260-88.2 C

7/ 1954 Goenng 260-28.5 A 12/1951 Sparks 260-28.5 A 5 ALLAN LIEBERMAN,Primary Examiner 4/1952 Young 260-28.5 A 5/1952 Young 260 285 A P. R.MICHL, Asslstant Exammer 10/1953 Young 260-28.5 A CL 3/ 1942 Smyers260-36 3/1959 Reding AV 10 260-4 R, 28.5 AV, 28.5 AS, 888, 896

